struct sockaddr_in * getAddr(int port, const char *ip);
int create_ip_multicast_sender_socket(const char *ip);
int create_ip_multicast_receiver_socket(const char *multicast_ip, const char *self_ip, const int port);
int ipmulti_send(int sock, inst *i_msg, int msg_size, struct sockaddr_in* addr);
